1. Technical Field
The present invention relates to method of packet communication in radio communication using TCP protocol and particularly to such method allowing normal communication to be rapidly recovered after communication interruption has occurred.
2. Related Art
Recent popularization of cellular phone and internet is hastening development of high speed radio communication technique. The inventors also have already developed high speed radio access systems serving as local and nonlocal area systems and achieved transmission rate of 156 Mbps.
However, radio communication may sometimes suffer from decrease of transmission rate due to interruption of communication. Particularly in system adopting millimeter wave band which attract attention of those skilled in the art as frequency resource in future, such wave band is readily affected by shadowing even by human body or the like. Accordingly, it is important not only to prevent communication interruption from occurring due to such shadowing but also to minimize affection of such shadowing.
TCP adopted also by internet provides perfect error control as well as flow control so that retransmission may be started upon recovery of communication interruption.
Retransmission by TCP has conventionally assumed that packet loss occurs due to congestion and often taken much time for retransmission against a plurality of continuous packet losses which are prone to occur due to wireless communication interruption. Consequently, TCP communication has often been disabled for a period longer than the period of communication interruption in wireless link layer.
To overcome this problem, several studies on radio environment accommodating TCP have been reported. For example, according to snoop protocol described in H. Balakrishnan, S. Seehan and R. H. Katz, “Improving ReliableTransport and Handoff Performance in Cellular Wireless Networks”, ACM Wireless Networks 1(4), December, 1995, base transceiver station is provided with agent adapted to monitor respective connections and in response to request for retransmission from radio terminals to absorb and respond by proxy so as to prevent transmission rate from being decreased due to retransmission.
However, such method of prior art has not been effective to control the errors continuously occurring for a period longer than a certain period due to communication interruption. In addition, the arrangement in which the base transceiver station is provided with the agent or both server and clients are modified is too complex to arrange and increases cost.
None of the conventional techniques offers effective method to solve these problems still remaining as barriers against the above described high speed radio communication techniques.
In view of the problems left behind by the prior art as have been described above, the present invention aims to provide a method of packet communication and a proposal node allowing retransmission to be rapidly started upon recovery of communication so as to compensate continuous packet losses due to communication interruption substantially without modification of the existing system and thereby contributing to simplification of arrangement and reduction of cost.